The present embodiments relate to curable phase-change ink compositions characterized by being solid at room temperature and molten at an elevated temperature at which the molten ink is applied to a substrate. These solid ink compositions, generally comprising an ink vehicle and a colorant, can be used for ink jet printing. The present embodiments are directed to a novel high gloss, ultraviolet (UV) curable, phase change ink composition comprising a colorant and an ink vehicle comprising a gellant, a reactive diluent, e.g., monomer or co-monomer, a photoinitiator package, and a curable wax.
Ink jet printing processes may employ inks that are solid at room temperature and liquid at elevated temperatures. Such inks may be referred to as solid inks, hot melt inks, phase change inks and the like. In ink jet printing processes employing hot melt inks, the solid ink is melted by the heater in the printing apparatus and utilized (jetted) as a liquid in a manner similar to that of conventional ink jet printing. Upon contact with the printing recording medium, the molten ink solidifies rapidly, allowing the colorant to substantially remain on the surface of the recording medium instead of being carried into the recording medium (for example, paper) by capillary action, thereby enabling higher print density than is generally obtained with liquid inks. Advantages of a phase change ink in ink jet printing are thus elimination of potential spillage of the ink during handling, a wide range of print density and quality, minimal paper cockle or distortion, reduced print-through, and enablement of indefinite periods of nonprinting without the danger of nozzle clogging, even without capping the nozzles.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at room or ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording medium, the droplets quickly solidify to form a predetermined pattern of solidified ink drops.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes or pigments, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or pigment or a mixture of dyes or pigments. The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording medium (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the recording medium, so that migration of ink along the printing medium is prevented and dot quality is improved.
Radiation curable phase change inks generally comprise at least one curable monomer, a gellant, a colorant, and a radiation activated initiator, specifically a photoinitiator, that initiates polymerization of curable components of the ink, specifically of the curable monomer. U.S. Pat. No. 7,279,587 to Odell et al., the disclosure of which is totally incorporated herein by reference, discloses photoinitiating compounds useful in curable phase change ink compositions. U.S. Patent Publication 2007/0120910 to Odell et al., which is hereby incorporated by reference herein in its entirety, describes, in embodiments, a phase change ink comprising a colorant, an initiator, and an ink vehicle.
While the above conventional phase change solid ink technology is generally successful in producing vivid images and providing economy of jet use and substrate latitude on different substrates, such technology has not been satisfactory for applications requiring high gloss levels.
For example, U.S. Patent Publication Nos. 2010/0112232 and 2010/0227075, both to Belelie et al., disclose methods for producing images that are meant more for matte prints than high gloss prints, and U.S. Patent Publication Nos. 2010/0021698 and 2010/0112232, both to Chretien et al., disclose methods for varying gloss from print-to-print but such variation is not readily achieved within the same print. In addition, currently available UV curable, phase change inks have a certain level of substrate-matching ability with respect to gloss but cannot achieve the higher levels to be considered high gloss. Applications such as photo publishing, packaging requiring both glossy and matte finishes, and the like, require high and/or variable gloss levels. These applications are experiencing tremendous growth and, as such, there is a need to overcome the deficiencies of current phase change ink technology for use in such applications. While known compositions and processes are suitable for their intended purposes, a need remains for excellent robust quality inks with high and/or varying gloss levels.
Each of the foregoing U.S. Patents and Patent Publications are incorporated by reference herein. Further, the appropriate components and process aspects of the each of the foregoing U.S. Patents and Patent Publications may be selected for the present disclosure in embodiments thereof.